Bass Preamps. What's the Big Deal?

[Count Bassie]

I'm using an ART Tube EQ I got from a fellow TBer here as a preamp- I attach it to my mic stand via a home-made jig, plug in the bass, and run a patch cable from the Tube EQ back to a Crest FA-1201, to a cab. It all seems to work fine, though I have to push the EQ's Gain just a tad to bring it up to stage volume.

What is the real difference between a specified bass preamp and a separate active EQ box like the Tube EQ? Or a Sansamp... or any gain-boosting pedal? I realize the bass pre is a complete "all-in-one" thing for amplification, but am I missing something if I'm able to make the ART EQ box work? Would I really be better off with a dedicated bass preamp?

 

[KJung]

Much of it has to do with the output gain being powerful enough to drive a power amp to full volume. If a unit achieves that (whether it be mic preamp, a bass preamp, a DI, or a boost pedal), then it comes down purely to tone and EQ/features.

Many of the preamp/power amp combinations I've tried have been a disappointment. There is a certain logic to letting an expert engineer design a preamp and power amp into a single unit (i.e., amp head) that is expertly designed to have the components work optimally together in the smallest possible form factor, with hi pass filtering optimal for bass guitar built in, etc., etc. IMO there.

 

[Count Bassie]

Many of the preamp/power amp combinations I've tried have been a disappointment. There is a certain logic to letting an expert engineer design a preamp and power amp into a single unit (i.e., amp head) that is expertly designed to have the components work optimally together in the smallest possible form factor, with hi pass filtering optimal for bass guitar built in, etc., etc. IMO there.

This is where I'm being driven, finally. I've just done what I've done because of money considerations, but the next move will be a head. Yep, thanks for the sensible reply.

 

[chadds]

That was a sensible answer.
May I add that the subjective aspect of how good certain pres can make your sound cannot be ignored. Power amps are supposed to just amplify the signal. When you can select the pre that exactly sounds as buttery or transparent as you like it's a great pleasure. If you ignore this then it doesn't matter what bass you use either....or strings or shoelaces.

 

[AlleyCat]

Hey guys. I got one for ya... I need a mid-priced preamp for my 115 combo. Kinda want to keep it simple though. If I can, some compression, good eq, mabey distortion, but light on the effects. I can get my rig to sound pretty good for what it is, just looking for a little more depth... some growl if i'm lucky. Oh yeah, not a big pedal guy either... unless its clean looking. Is it out there??

 

[bgavin]

Count, if this is over simplified, please excuse my starting from the top.

A passive pickup such as the DiMarzio Model J produces about 150 mV.
The typical power amp has an input sensitivity of 1.0 to 1.9 volts.
Using 1.14v as the average input sensitivity of those amps in my spreadsheet, this is a 17.6 dB difference that must be made up by the preamp device.

The preamp can be a simple gain device such as the ART, or it can offer tone controls. The only requirement is a minimum of 17.6 dB gain for this scenario and sufficient output voltage.

You have to check your output voltage to make sure it is sufficient for your particular power amp. If your preamp does not provide sufficient output voltage (my SWR IOD) it will not drive the power amp to full power.

The ideal preamp input is impedance matched for your pickup output type. The output impedance of the preamp is matched to the input impedance of your power amp. For a passive-pickup preamp, this would be at least a megohm input, and low impedance output. Active pickups do not have the impedance loading problems inherent in passive.

 

[Count Bassie]

I'm going to have to get out my manuals for that bit of homework, but that's exactly the kind of info I'd like to know. Trouble with stuff is there are so many variables- manufacturers, kinds of stuff, etc.! But there was a definitivenmuber, and that I can relate to!

Thanks B., everyone.

 

[bongomania]

The "preamps explained" link in my sig expands on those numbers and gives some more info to go on.

I have been equally satisfied (or equally dissatisfied) with both bass-specific preamps and general-purpose "channel strip" preamps. As I note in my article, the first thing you have to do in any case is verify whether a given preamp has the actual input and output level and impedance capabilities you need; then you should look at whether the functions/controls are useful to you; and then, last, determine if you like the tone. Because the tone won't matter if it doesn't function well in your application.

This is a good argument for the all-in-one heads because they have taken care of all the level and impedance business already. But for those of us that have a technical inclination, or like to experiment, the separate component systems still have a strong appeal.

IME the two things that most commonly separate good bass-friendly preamps from not-so-great all-purpose pre's are (a) the EQ range of control, especially in the lows and low mids, and (b) the tonal color--warmth, fatness, growl--usually lacking in the all-purpose pre's.

 

[bongomania]

Hey guys. I got one for ya... I need a mid-priced preamp for my 115 combo. Kinda want to keep it simple though. If I can, some compression, good eq, mabey distortion, but light on the effects. I can get my rig to sound pretty good for what it is, just looking for a little more depth... some growl if i'm lucky. Oh yeah, not a big pedal guy either... unless its clean looking. Is it out there??

For growl and EQ you should check out the many products from Tech 21. They have several that might suit you. The BBE BMax might appeal to you too. Note that if you aren't getting enough "depth" now, adding a preamp will not help you at all. That is the combo amp limiting you there, and no bandaid fix will make it capable of the depth and fullness you're missing.

 

[Swift713]

+1 A lame speaker cabinet can spoil an otherwise great rig. The signal chain is only as strong as it's weakest link.